Newborn Direct Ethanol Biomarker
By Douglas Lewis, ScD, President and Scientific Director, USDTL
How can medical science accurately identify ethanol exposed newborns and do it in a manner timely enough to allow clinicians to take action and treat the ethanol affected babies to ameliorate the prenatal damage that the ethanol exposure may have produced? Since the first documentation of Fetal Alcohol Syndrome (FAS) and subsequent description of the continuum of Fetal Alcohol Spectrum Disorders (FASD), it has become increasingly imperative that newborns exposed to significant amounts of ethanol be diagnosed as early as possible and then treated early and intensively while the brain is most plastic and capable of new growth.
Historically, maternal self-report of ethanol consumption has been the principal means of obtaining fetal ethanol exposure histories. Maternal self reports, however, suffer from under reporting due to maternal shame, fear of potential consequences and reporting bias. The problems of self-report have been known for many years so a series of indirect markers of ethanol exposure were developed. These markers are actually somewhat non-specific markers of organ pathology that ethanol toxicity is the most likely agent, but not with any certainty. Of the many indirect pathological markers such as GGT, ALT, MCV, and CDT, CDT is considered the most specific but is less sensitive in women and of little value in umbilical cord blood, so it may not offer much over self-report for histories in pregnancy.
The direct biomarkers, on the other hand, are not indirect measures of pathological damage but are direct measures of the non-oxidative metabolites of ethanol. These non-oxidative metabolites represent less than 1% of the total ethanol consumed, but since ethanol is consumed in hundreds of grams over time, the metabolites can reach significant and measurable concentrations in a variety of tissues.
The first direct ethanol biomarkers to be seriously studied in the newborn were the fatty acid ethyl esters (FAEE), a series of ethyl esters of various fatty acids that were known to be found in serum of adult individuals after consuming ethanol. Indeed, FAEE’s do appear in the meconium of newborns. Unfortunately, FAEE’s appear at low concentrations in nearly all newborns and thus required establishing a threshold level that would provide unequivocal evidence of ethanol consumption. This issue which reduced the sensitivity to about 60%, as well as the discovery that meconium, when exposed to ethanol post-passage, would synthesize FAEE’s in vitro introduced additional variables to interpretation. When coupled with the successful collection rate of only 70 – 80% of newborn cases, FAEE meconium analysis lacks sensitivity, specificity and universality for general use.
Another direct ethanol biomarker, Ethyl Glucuronide (EtG) also has been analyzed in meconium. While promising, the same lack of universality due to low collection rate for meconium applies here as well. EtG, however, has been analyzed in two much more universally available tissues, placenta and umbilical cord tissue in two separate laboratories in Italy and in the USA. Both labs have confirmed the utility of using EtG in these related tissues as a sensitive and specific marker for fetal alcohol exposure. EtG is currently the most reliable universally available ethanol biomarker available for diagnosing newborn ethanol exposure despite some gaps in the knowledge base. More research is needed to further define the level of drinking required to produce a positive and the time window reflected by a positive.
Much has been accomplished in the past twenty years to bring truly useful diagnostic tools such as the direct biomarker EtG in placenta and umbilical cord tissue to clinicians who desire to treat newborns exposed to high levels of ethanol during pregnancy. Much work remains to be done to further the prognostic evaluations beyond just the diagnostic of fetal ethanol exposure and assist the clinicians with an understanding of the severity of the syndrome at the earliest possible moment. As we explore the various improvements in separation science and genetics, more breakthroughs are coming as we continue to push the frontiers of this rapidly developing area of toxicology.
USDTL has made significant progress in laboratory detection of heavy fetal alcohol exposure through the use of Phosphatidylethanol (PEth) analysis of newborn blood spots. This ground-breaking achievement utilizes a universally available specimen thereby removing a major barrier of sample availability in identification of exposed newborns. A further challenge, however, is to determine the extent of damage that ethanol exposure may have caused. To explore the means to this diagnostic information, USDTL has launched a new area of research with the addition of Aileen Baldwin, Ph.D., M.P.H. Dr. Baldwin comes to USDTL following a post-doctoral fellowship at the Pasteur Institute in Paris, France and obtained her Ph.D. in Molecular Biology and Masters in Public Health at Northwestern University. Dr. Baldwin recently submitted a Phase I SBIR grant application to the NIH to investigate epigenetic changes in DNA from blood spots of newborns identified to have been exposed to excessive levels of ethanol as determined by detection of PEth in their blood spots.